The principal objective of this study is to investigate the relationship between cigarette smoking and hepatocellular carcinoma (HCC). The effect of cigarette smoking on HCC risk will be estimated separately for cases who are negative for markers of hepatitis B virus (HBV) infection and those who are positive for markers of HBV infection. Other possible risk factors for HCC will also be examined. Blood will be drawn from each study subject and classified according to the presence of markers of HBV infection. This will enable us to measure the prevalence of HBV infection among cases and controls and to estimate the magnitude of the risk of HCC associated with HBV infection. A detailed alcohol history will also be obtained from study subjects. We will therefore be able to test for a possible association between alcohol consumption and HCC risk, controlling for possible confounding by cigarette smoking. An occupational history will be obtained from each study and occupations in which exposure to suspected hepatocarcinogens is probable will be identified and subjects classified accordingly. A drug history will also be obtained from each study subject and the hypothesis that oral contraceptive use increases HCC risk will be evaluated. This will be a case-control study. Data will be obtained by interviewers using a standard questionnaire for both cases and controls. Only newly diagnosed cases will be included and controls will be selected from the hospital.